Jet inks commonly contain water, an organic co-solvent, such as tetraethyleneglycol, one or more dyes dissolved in the water, and a surfactant to facilitate penetration of the ink. The dyes are typically soluble in a basic solution and the ink contains a base such as ammonia, which leaves the ink after printing, leaving a printed dye resistant to ordinary water (termed waterfast printing). Other standard ingredients are a chelant for mineral control, such as tetrasodium ethylene diamine tetraacetic acid, a wetting agent such as glycerol, a biocide, and buffers, such as equal parts of sodium phosphate and sodium tetraborate. U.S. Pat. No. 5,352,283 to Beach et al has inks which incorporate much of such prior art. This invention also employs the same black dye as employed as the single dye in the embodiments of the foregoing patent 5,352,283. That dye is the direct subject of U.S. Pat. No. 5,198,002 to Aulick et al. U.S. Pat. No. 5,062,892 to Halko discloses buffers such as used in these formulations.
This invention employs an ethoxylated amine surfactant believed to be a novel incorporation in jet inks. The jet inks print conventionally with minimal splatter or separation into small adjoining dots (which will be termed satellites).
The novel surfactant is a tertiary dipolyethoxylated amine with the third substituent being a long chain organic moiety having no functional group or only ester and carboxylic acid functional groups. Trispolyoxylated amines in jet inks are disclosed in U.S. Pat. No. 5,389,134 to Breton et al. No comparable prior art with respect to the novel surfactant of this invention is known.
A prior art ink comparable in performance to the ink of this invention has a static surface tension of more than 45 dynes/cm and a dynamic surface tension of about 65 dynes/cm. The ink of this invention has a static surface tension of less than 40 dynes/cm and a dynamic surface tension also of about 65 dynes/cm.